1. Field of Invention
The present invention relates to a water treatment agent.
2. Description of Related Arts
With the thriving of industrial and farming industry, a large amount of poisonous and toxic refractory organic pollutants are discharged into the water system, resulting in a heavy pollution of the surface water and ground water and making the water quality getting worse and worse. Currently, a common solution is to employ an oxidizing process to remove the organic pollutants in water using oxidization agent such as chlorine, chlorine dioxide, hydrogen peroxide, ozone, potassium permanganate and so on. Accordingly, the redox potential of chlorine, chlorine dioxide, hydrogen peroxide, ozone and potassium permanganate is 1.36V, 1.50V, 1.77V, 2.07V and 1.69V respectively.
It is recognized that ozone is advantageous with the highest redox potential, the strongest oxidability and is also friendly to aqueous solution, but the investment and cost for maintaining the oxidizing process is relatively high. Although the oxidability of hydrogen peroxide itself is not very strong, high active hydroxyl radicals will be produced when hydrogen peroxide is simultaneously present with Fe(II) in an acidic condition, thus providing a strong oxidability (with a typical redox potential of 2.8V). However, the pH value of the aqueous reaction system should be monitored and adjusted during the whole reaction process, making the process very complicated and hard to control. Chlorine dioxide is a strong disinfectant, but during the reaction with organic substance, it is reduced to provide chlorous ion which is destructive to human red blood cells. Thus, there is a safety risk for the use of chlorine dioxide. Chloride does oxidize the organic substance to some extent and has long been employed as a pretreatment oxidization agent for water treatment. However, chloride reacts with various kinds of organic pollutants and produces a lot of halogenated byproducts which are harmful to human body. Therefore, the use of chloride for pretreatment is gradually restricted in practice.
Potassium permanganate has a relatively higher oxidability for removing the organic pollutants in water and does not produce poisonous and toxic byproducts. Furthermore, the cost for the basic infrastructure is relatively low, the requirement for the equipment is not very high and it is also convenient for operation and management. Therefore, potassium permanganate is a preferred choice in practice. However, potassium permanganate has a high selectivity and can only remove organic substance with unsaturated functional groups such as alkene and phenol. In other words, potassium permanganate has a low activity for oxidization of poisonous and toxic refractory organic pollutants. But high active intermediate manganese is produced during the oxidization process. Accordingly, the intermediate manganese has a relatively high redox potential and reacts quickly so as to degrade organic substance. But the high active intermediate manganese exists in a very short period of time and may decompose itself. Therefore, the effective utilization rate is low and the oxidization ability of the intermediate manganese need to be exploited.